Prop Designer blog

The main part of this site has nearly 250 pages. There are a number of ways to navigate the site, you can use the buttons down the side, the text hyperlinks at the bottom of the screen or there is a site navigation page that acts like a contents page for a book. There is also a set of links just under the banner that enable a user to back out of the page to the level above. Sometimes a set of related pages are linked togeter with a forward/backward/up set of arrows.

I would hope this is enough linking to find what you want on the main site. Some of the linking is missing on other parts of the site, particularly the Library. Although the layout is relatively simple, someone may choose to use an aerofoil designed for another part of the plane or modify one for another use. Human Powered Flying, http://www.humanpoweredflying.propdesigner.co.uk/ is mostly hyperlinked although it has a contents page.

Although there is no index, Google and Yahoo! (Other seach engines are available) effectively supply an index as this is a way many users find the site.

As always if you have any comments please let me know.

As I’m sure you realize this site is written in English. It is written in English English as opposed to American English although Britain represents a minority of visitors. The USA represents about a quarter of visitors and I suspect the majority of other visitors that read English have been taught the American version. My spelling is not that good so I tend to rely on spell checkers that are likely to be American. At some point in the future even the Monarch is likely to be speaking American English.

I don’t know if you realize it but the site also attempts to simplify the use of English so that it is more likely to be translated by the automated translators not to mention I try to make allowances for the intended audience of less technical people so jargon is kept to a minimum. If this is not the case then, as always, let me know.

I replaced the power supply in my computer and it is working again! The man in the computer shop said there had been an increased number of computer power supplies failing last week so mine was not the only computer to fail in this way.

Now I have the computer back I can get at all my e-mails and update the web site.

I have to apologise as the web site will not be updated for any reason for the next few days at least as there has been a death in the family.

I went out for the day on Wednesday and when I came back in the evening I tried to turn on my computer and.. it was dead. It remains dead for some reason and I have yet to find the cause of death.

I initially thought that just the on/off switch had failed and it would be possible to override the switch by shorting out the connections on the motherboard which  had done on a previous computer but this did not work. This is about the limit of my knowledge of fixing computers although The computer has already had the motherboard replaced after I damaged the original one adding some RAM.

I have borrowed my wife’s laptop to write this blog and check e-mail accounts but all the website is on the other computer without a proper backup so that will all have to wait until I have fixed my main computer somehow. Please be patient.

I now host a new section on Airglow at http://airglow.propdesigner.co.uk/ and I am about to add some photos of Abhilasha at http://pictures.propdesigner.co.uk/html/abhilasha.html some time over the weekend if all goes well and it got me thinking about over-engineering. Abhilasha is a marvelous achievement but it turned out heavier than the designer would have liked, Airglow is probably slightly heavier than it needs to be just to fly but it has been around for nearly 20 years.

Abhilasha uses standard components like standard Aluminium alloy tubing, steel bolts and plywood fittings among other components resulting in a relatively cheap and easy to build aircraft but 15 to 20 Kg overweight. Airglow uses Carbon fibre to reduce it’s weight and plastic ribs that has resulted in a robust aircraft (for a HPA) that has not deteriorated much over it’s long lifetime.

I am not sure Airglow was designed to last as long as it has but I believe it was designed with an extended life compared to previous HPAs that have had lives measured in years rather than decades and it has been used in research.

Thankyou for reading this blog and thankyou for visiting this site and making it as popular as it is. There has been over 13,000 hits on the site according to the site’s statistics this month. The number of hits has grown steadily since the site was first created nearly 4 years ago. I get people vititing the site from Argentina to Zimbabwe but mostly from the United States, United Kingdom, Singapore, Australia, Netherlands and Japan.

Are there many people interested in human powered flight? I doubt it, there is information about a wide variety of subjects and I have to say, some people accidentally come to the site expecting to find something entirely different, for example, a person came to the site trying to find the wingspan of a Toucan and was probably rather confused to find it was 139 feet, about 42 metres, a very big bird.  Other people are trying to find information about aerodynamics, engineering and structures in general and do not care that it is related to human powered aircraft.

There are 5 references to this site from Wikipedia, one of which used to go to a non-existent page until I added it and redirect users to the correct page. There should be more as some information in the Czech version of Wikipedia is from the site.

I am pleased with the site but I will try to make the site better by adding more and relevant content.

For those who don’t know, an ornithoper is an aircraft that uses an animal-like way to fly, usually flapping wings.

The University of Onterio is building a human powered ornithopter to fly the classic figure of eight Kremer prize course to prove the concept. The ornithopter is based on work on a powered ornithopter that flew once and then they had to add a jet engine. The flight lasted 14 seconds and was terminated due to lack of control.

I don’t have high hopes for it ever taking off under it’s own power but… what do I know?

I noticed the site had a visit from www.army.mil . Does this mean the US. army is interested in human powered flight? I am told that the army has some software that searches the web much like Google but it is looking for terrorist materials and links with Al-Qaeda. I think they will have to work hard to create non-existent links between what I do and any terror organization.

I occasionally tweek all or part of the web site to improve them, at least I hope they are improvements. I have added links to news, this blog and the forum to the library part of the site. The gallery needs similar links adding and I will have to ask if Chris Roper would also like the links added to his book at http://humanpoweredflying.propdesigner.co.uk/.

A full redesign of the site would take some time and is not something I feel like doing just yet.

One of the most popular searches on my web site is for the NACA 0012 and some coordinates for it. I also have the NACA 0009 section, the NACA 0021 section as well as a number of others on the site.

Pushing my mathematical powers to the limit I noticed that the thickness of these sections were divisible by 3 and I wondered why this was. The answer dates back to the 1940’s and 50’s. Aerofoil section data was hard to get and without computers or access to wind tunnels designing your own was generally not an option so you had to find a source of data. The easiest and most common source was “Theory of wing sections” with a subtitle of “ including a summary of airfoil data” by Ira H. Abbott and Albert E. Von Doenhoff. The appendicies provide a lot of data on NACA aerofoils and they are of various thicknesses all divisible by 3! This was often the source for early HPA designers

With computers it is possible to design your own aerofoil section or even take a NACA section and change it’s thickness to 10, 11 or even 11.5% thickness if you think it is appropriate.